基于伪码与多普勒频率分离的北斗信号捕获算法

北斗B1频点信号采用二次编码结构，而二次编码使用的NH（Neumann-Hoffman）码会发生比特跳变，导致接收机捕获性能降低，对此，提出一种基于伪码与多普勒频率分离的北斗信号捕获算法.该算法将接收信号分为两路，利用延迟差分运算和测距码的双极性分别对两路信号进行处理，消除了NH码比特跳变带来的影响.在此基础上使用匹配滤波器捕获码相位，使用快速傅里叶变换搜索多普勒频移，实现了码相位和多普勒频移的同时捕获.仿真结果表明，提出的算法成功捕获到了NH码跳变的信号，且在相同虚警率下灵敏度相比部分匹配滤波和快速傅里叶变换算法约有1.03 dB的提升.

Beidou Signal Capture Algorithm Based on Pseudo Code and Doppler Frequency Separation

Beidou B1 frequency signal using the secondary encoding structure, bit-flipping of Neumann-Hoffman (NH) codes used for secondary encoding leads to a decrease in receiver acquisition performance. Aiming at this problem, a Beidou signal acquisition algorithm based on pseudocode and Doppler frequency separation is proposed. The algorithm divides the received signal into two paths, and uses the delay difference operation and the bipolarity of the ranging code to process the two signals respectively, thus eliminating the influence of the bit hopping of the NH code. Based on this, the matched filter is used to capture the phase of the code and the fast Fourier transformation is used to search for the Doppler frequency. Capturing the phase and the Doppler frequency at the same time is realized. Finally, the simulation results show that the proposed algorithm successfully captures the signal with bit-flipping. Compared to partial matched filtering-fast Fourier transformation algorithm, the sensitivity is 1.03 dB increased under the same false alarm rate.